β-Aminoenones have three functional groups, i. e. amino, double bond, and carbonyl, and show the characteristic behaviors of these groups. They also behave as vinylogues of amide as well as enamine or enone. Moreovere, β-aminoenone has four geometrical isomers, trans-s-cis, trans-s-trans, cis-s-cis, and cis-s-trans. From these points of view, β-aminoenones are much interesting in synthetic, physicoorganic, biological, and pharmaceutical works. Recently, a number of papers on β-aminoenones have reported. This review containes the syntheses, reactions, and properties of β-aminoenones.
The synthesis of exoalkylidenes were accomplished via the formation of aziridinium ylid from carbonyl derivatives. The name “Azyl” reaction was proposed. Azyl reaction gave exoalkylidene derivatives in better yield with simpler process than the use of triphenylphosphine alkylidenes. The hindered or highly enolizable ketones were also converted easily to exomethylene derivatives.
Preparation, structure and chemistry of sulfuranes are reviewed as follows ; 1) sulfurane as a reaction intermediate in which are described the possible formation and indirect approval method of sulfurane during the reactions of sulfonium salts, and sulfilimines with nucleophiles, 18O exchange reactions of sulfoxides and some sulfide-halogen complexes. 2) the isolated sulfuranes in which both Kapovits's and Martin's novel sulfuranes are described. Some reactions using these sulfuranes are also summarized, 3) sulfide halagen complexes which have previously been thought to be sulfuranes but mostly the complexes isolated are either the onium salts or charge transfer complexes. The preparations and reactions of the complexes are described.
As a part of series of investigation of the Wallach rearrangement, the reactions of various azoxybenzene derivatives with chlorosulfuric and polyphosphoric acid were studied and compared with the Wallach rearrangement using sulfuric acid. The following results were obtained. (1) The reactivity of azoxybenzene derivatives toward these acids is dependent on their acidity function ; chlorosulfuric>sulfuric>polyphosphoric acid. (2) The reaction of azoxybenzene derivatives with chlorosulfuric acid generally gives hydroxyazobenzenes in higher ortho-para ratios than that in the case of the Wallach rearrangement using sulfuric acid. Azoxybenzene derivatives having electron-releasing group tend to give the corresponding azobenzenes in high yield. (3) With polyphosphoric acid, the reactivity of azoxybenzenes depended on the acidity function reported by Downing et al., and higher ortho-para ratios and lower yield of azo compounds were generally recognized in comparison with the Wallach rearrangement using sulfuric acid.
On the alkylenation of hydroquinone (1a), hydroquinone monomethyl ether (1b), resorcinol (1c), resorcinol monomethyl ether (1d), catechol (1e) and guaiacol (1f), the corresponding alkylenated ethers were obtained in good yields using ethylene chloride or 1, 3-dichloropropane as alkylenation reagent in aprotic polar solvents where concentrations of (1af) were regulated to be low.